GLOBAL JOURNAL OF EARTH AND ENVIRONMENTAL SCIENCE
Integrity Research Journals

ISSN: 2636-6002
Model: Open Access/Peer Reviewed
DOI: 10.31248/GJEES
Start Year: 2016
Email: gjees@integrityresjournals.org


Integrating chemostratigraphy in the modification and improvement of well correlation in the offshore Niger Delta

https://doi.org/10.31248/GJEES2024.206   |   Article Number: B1273E732   |   Vol.10 (4) - August 2025

Received Date: 08 July 2025   |   Accepted Date: 15 August 2025  |   Published Date: 30 August 2025

Authors:  Ihunda, C. E.* , Selegha Abrakasa and Soronnadi-Ononiwu, G. C.

Keywords: geochemistry, Chemostratigraphy, trace elements, Miocene, palaeogeography.

The Niger Delta is a stratigraphically complex fluvial system of Tertiary age. A total of 15 ditch cutting samples were obtained within the interval of interest, from which 3 wells were subjected to inorganic geochemical and mineralogical analysis to determine the major and trace element concentrations. Inferences from the results show that the Agbada Formation is divided into four Chemostratigraphic mega zones, 12 geochemical units and 9 sand units with geochemical boundaries for DS well at depths of 12,300 ft to 13,500 ft and 7,840 ft to 8,660 ft for ML 1 Well, and ML 2 well at depth 13,240 ft to 14,530 ft. Changes in values of Ga/Rb and Al2O3/(CaO+ MgO+K2O+Na2O) indicate warmer paleoclimate and increasingly intense hydrolytic weathering, marking a sustained change in the paleoclimate. The high percentage concentration of Al2O3 is an indication of abundant clay minerals, whereas the high concentration of Zr suggests sedimentary reworking of the sediments. High V/Ni against Co/Mo ratio concentration intensified upwelling, particularly in those restricted depths was favoured by palaeogeography and significant fluvial input. Conditions could readily evolve from poorly oxygenated to anoxic, the latter state being geochemically the most significant condition. The major oxides trace elements revealed four chemostratigraphic boundaries for DS. ML 1 and ML 2 wells, respectively. The information from V/Sc, Ni/V and V/(V+Ni) ratios indicates the prevalence of anoxic conditions. The redox-sensitive trace elements of the shaly middle parts of the well suggest dysoxic–anoxic conditions, and in most parts of the ML 2 well. Ratios of SiO2 and Al2O3 correspond to sedimentary facies, namely sandstone, siltstone and claystone, while variation in ratios of Cd/Ba and Al2O3/(Na2O+CaO+K2O+MgO) depicts fluctuating paleoclimate during the deposition of the sedimentary sequence. Geochemical values of Cr/Al2O3, Cr/Na2O and Nb/Al2O3 relate to changes in sediment provenance and indicate that during deposition, the provenance became more mafic and less intermediate. The chemostratigraphic correlation is more detailed than is available from other stratigraphic techniques.

Abrakasa, S., Okechukwu, N., & Edikan, S. (2020). General Chemostratigraphy of the formations in Well M, Offshore Senegal. International Journal of Scientific Research and Engineering Development, 3(6), 2581-7175.
 
Akaegbobi, I. M., & Ogungbesan, G. O. (2016). Geochemistry of the Paleocene limestones of Ewekoro Formation, eastern Dahomey Basin, southwestern Nigeria: implication on provenance and depositional conditions. Ife Journal of Science, 18(3), 669-684.
 
Algeo, T. J., & Maynard, J. B. (2004). Trace-element behavior and redox facies in core shales of Upper Pennsylvanian Kansas-type cyclothems. Chemical Geology, 206(3-4), 289-318.
https://doi.org/10.1016/j.chemgeo.2003.12.009
 
Aplin, A. C. (1993). The composition of authigenic clay minerals in recent sediments: Links to the supply of unstable reactants. In: Manning, D. A. C., Hall, P. L., & Hughes, C. R. (eds.). Geochemistry of clay-pore fluid interactions. Chapman and Hall. Pp. 81-106.
 
Armstrong-Altrin, J. S., Lee, Y. I., Verma, S. P., & Ramasamy, S. (2004). Geochemistry of sandstones from the Upper Miocene Kudankulam Formation, southern India: implications for provenance, weathering, and tectonic setting. Journal of sedimentary Research, 74(2), 285-297.
https://doi.org/10.1306/082803740285
 
Avbovbo, A. A. (1978). Tertiary lithostratigraphy of Niger Delta. Amerian Association of Petroleum Geologists Bulletin, 62(2), 295-300.
https://doi.org/10.1306/C1EA482E-16C9-11D7-8645000102C1865D
 
Bhatia, M. R. (1983). Plate tectonics and geochemical composition of sandstones. The Journal of geology, 91(6), 611-627.
https://doi.org/10.1086/628815
 
Breit, G. N., & Wanty, R. B. (1991). Vanadium accumulation in carbonaceous rocks: a review of geochemical controls during deposition and diagenesis. Chemical Geology, 91(2), 83-97.
https://doi.org/10.1016/0009-2541(91)90083-4
 
Brumsack, H. J. (2006). The trace metal content of recent organic carbon-rich sediments: Implications for Cretaceous black shale formation. Palaeogeography, Palaeoclimatology, Palaeoecology, 232(2-4), 344-361.
https://doi.org/10.1016/j.palaeo.2005.05.011
 
Calvert, S. E., & Pedersen, T. F. (2007). Chapter fourteen elemental proxies for palaeoclimatic and palaeoceanographic variability in marine sediments: interpretation and application. Developments in Marine Geology, 1, 567-644.
https://doi.org/10.1016/S1572-5480(07)01019-6
 
Chamley, H. (1989). Clay Sedimentology. Springer Verlag, Berlin. p.623.
https://doi.org/10.1007/978-3-642-85916-8
 
Childress, M., & Grammer, G. M. (2015). High resolution sequence stratigraphic architecture of a mid-continent Mississippian outcrop in southwest Missouri. Shale Shaker. Pp. 206-234.
 
Churchman, G. J. (2000). The alteration and formation of soil minerals by weathering. In: Summer, M.E. (ed.), Handbook of soil science. CRC Press, New York. 1, F3-27.
 
Cox, R., Lowe, D. R., & Cullers, R. L. (1995). The influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern United States. Geochimica et Cosmochimica Acta, 59(14), 2919-2940.
https://doi.org/10.1016/0016-7037(95)00185-9
 
Craigie, W. N. (2018). Principles of elemental chemostratigraphy. Cham: Springer.
https://doi.org/10.1007/978-3-319-71216-1
 
Doust, H., & Omatsola, E. (1990). Niger Delta. In: Edwards, J. D., & Santogrossi, P. A. (eds.), Divergent/passive margin basins, American Association of Petroleum Geologists Memoir, 48, 201-239
https://doi.org/10.1306/M48508C4
 
Ehinola, O. A., Ejeh, O. I., & Oderinde, O. J. (2016). Geochemical characterization of the Paleocene Ewekoro limestone formation, SW Nigeria: implications for provenance, diagenesis and depositional environment. Geomaterials, 6(3), 61-77.
https://doi.org/10.4236/gm.2016.63006
 
Ejedawe, J. E., Coker, S. J. L., Lambert-Aikhionbare, D. O., Alofe, K. B., & Adoh, F. O. (1984). Evolution of oil-generative window and oil and gas occurrence in Tertiary Niger Delta Basin. American Association of Petroleum Geologists Bulletin, 68(11), 1744-1751.
https://doi.org/10.1306/AD46198F-16F7-11D7-8645000102C1865D
 
Evamy, B. D., Haremboure, J., Kamerling, P., Knapp, W. A. Molloy, F. A. and Rowlands, P.H. (1978). Hydrocarbon habitat of Tertiary Niger Delta. American Association of Petroleum Geologists Bulletin 62, 1-39.
https://doi.org/10.1306/C1EA47ED-16C9-11D7-8645000102C1865D
 
Frankl, E. J., & Cordry, E. A. (1967). The Niger Delta oil province: Recent development onshore and offshore. In Seventh World Petroleum Congress Proceedings, Mexico, 2, 195-209.
 
Fu, X., Wang, J., Chen, W., Feng, X., Wang, D., Song, C., & Zeng, S. (2016). Elemental geochemistry of the early Jurassic black shales in the Qiangtang Basin, eastern Tethys: constraints for palaeoenvironment conditions. Geological Journal, 51(3), 443-454.
https://doi.org/10.1002/gj.2642
 
Garver, J. I., Royce, P. R., & Scott, T. J. (1994). The presence of ophiolites in tectonic highlands as determined by chromium and nickel anomalies in synorogenic shale: Two examples from North America. Russian Geology and Geophysics, 35(2), 1-8.
https://doi.org/10.2113/RGG.1994.35.2.1
 
Garver, J. I., Royce, P. R., & Smick, T. A. (1996). Chromium and nickel in shale of the Taconic foreland; a case study for the provenance of fine-grained sediments with an ultramafic source. Journal of Sedimentary Research, 66, 100-106.
https://doi.org/10.1306/D42682C5-2B26-11D7-8648000102C1865D
 
Ghandour, I. M., Masuda, H., & Maejima, W. (2003). Mineralogical and chemical characteristics of Bajocian-Bathonian shales, G. Al-Maghara, North Sinai, Egypt: climatic and environmental significance. Geochemical Journal, 37(1), 87-108.
https://doi.org/10.2343/geochemj.37.87
 
Haack, R. C., Sunderaman, P., Diedjomahor, J. O., Xiao, H., Gant, N. J., May, E. D., & Kelsch, K., 2000. Niger Delta Petroleum System, Nigeria. In: Mello, M. R. & Kat, B. J. (eds). Petroleum Systems of South Atlantic Margins. Tulsa: America Association of Petroleum Geologist. Pp. 213-231.
https://doi.org/10.1306/M73705C16
 
Hallam, A., Grose, J. A., & Ruffell, A. H. (1991). Palaeoclimatic significance of changes in clay mineralogy across the Jurassic-Cretaceous boundary in England and France. Palaeogeography, Palaeoclimatology, Palaeoecology, 81(3-4), 173-187.
https://doi.org/10.1016/0031-0182(91)90146-I
 
Hatch, J. R., & Leventhal, J. S. (1992). Relationship between inferred redox potential of the depositional environment and geochemistry of the Upper Pennsylvanian (Missourian) Stark Shale Member of the Dennis Limestone, Wabaunsee County, Kansas, USA. Chemical Geology, 99(1-3), 65-82.
https://doi.org/10.1016/0009-2541(92)90031-Y
 
Hiscott, R. N. (1984). Ophiolitic source rocks for Taconic-age flysch: trace-element evidence. Geological Society of America Bulletin, 95(11), 1261-1267.
https://doi.org/10.1130/0016-7606(1984)95<1261:OSRFTF>2.0.CO;2
 
Hou, H., Shao, L., Li, Y., Liu, L., Liang, G., Zhang, W., Wang, X., & Wang, W. (2022). Effect of paleoclimate and paleoenvironment on organic matter accumulation in lacustrine shale: Constraints from lithofacies and element geochemistry in the northern Qaidam Basin, NW China. Journal of Petroleum Science and Engineering, 208, 109350.
https://doi.org/10.1016/j.petrol.2021.109350
 
Islam, M. R., Stuart, R., Risto, A., & Vesa, P. (2002). Mineralogical changes during intense chemical weathering of sedimentary rocks in Bangladesh. Journal of Asian Earth Sciences, 20(8), 889-901.
https://doi.org/10.1016/S1367-9120(01)00078-5
 
Jia, J., Bechtel, A., Liu, Z., Strobl, S. A., Sun, P., & Sachsenhofer, R. F. (2013). Oil shale formation in the Upper Cretaceous Nenjiang Formation of the Songliao Basin (NE China): Implications from organic and inorganic geochemical analyses. International Journal of Coal Geology, 113, 11-26.
https://doi.org/10.1016/j.coal.2013.03.004
 
Jones, B., & Manning, D. A. (1994). Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones. Chemical Geology, 111(1-4), 111-129.
https://doi.org/10.1016/0009-2541(94)90085-X
 
Kronberg, B. I., & Nesbitt, H. W. (1981). Quantification of weathering, soil geochemistry and soil fertility. Journal of Soil Science, 32(3), 453-459.
https://doi.org/10.1111/j.1365-2389.1981.tb01721.x
 
Lane, H. R., & De Keyser, T. L. (1980). Paleogeography of the late Early Mississippian (Tournaisian 3) in the central and southwestern United States. Paleozoic Paleogeography of West-Central United States: Rocky Mountain Paleogeography Symposium 1, pp. 149-162.
 
Letnikova, E. F., & Geletii, N. K. (2005). Vendian-Cambrian carbonate sequences in sedimentary cover of the Tuva-Mongol microcontinent. Lithology and Mineral Resources, 40(2), 167-177.
https://doi.org/10.1007/s10987-005-0017-9
 
Lewan, M. D. (1984). Factors controlling the proportionality of vanadium to nickel in crude oils. Geochimica et Cosmochimica Acta, 48(11), 2231-2238.
https://doi.org/10.1016/0016-7037(84)90219-9
 
Li, L., Liu, Z., George, S. C., Sun, P., Xu, Y., Meng, Q., ... & Wang, J. (2019a). Lake evolution and its influence on the formation of oil shales in the Middle Jurassic Shimengou Formation in the Tuanyushan area, Qaidam Basin, NW China. Geochemistry, 79(1), 162-177.
https://doi.org/10.1016/j.geoch.2018.12.006
 
Li, M., Shao, L. Y., Liu, L., Lu, J., Spiro, B., Wen, H. J., & Li, Y. H. (2016). Lacustrine basin evolution and coal accumulation of the Middle Jurassic in the Saishiteng coalfield, northern Qaidam Basin, China. Journal of Palaeogeography, 5(3), 205-220.
https://doi.org/10.1016/j.jop.2016.03.001
 
Li, Y., Sun, P., Liu, Z., Xu, Y., Liu, R., & Ma, L. (2021). Factors controlling the distribution of oil shale layers in the Eocene Fushun Basin, NE China. Marine and Petroleum Geology, 134, 105350.
https://doi.org/10.1016/j.marpetgeo.2021.105350
 
Li, Y., Wang, Z., Gan, Q., Niu, X., & Xu, W. (2019b). Paleoenvironmental conditions and organic matter accumulation in Upper Paleozoic organic-rich rocks in the east margin of the Ordos Basin, China. Fuel, 252, 172-187.
https://doi.org/10.1016/j.fuel.2019.04.095
 
Madukwe, H. Y., & Bassey, C. E. (2015). Geochemistry of the Ogwashi-Asaba Formation, Anambra Basin, Nigeria: Implications for provenance, tectonic setting, source area weathering, classification and maturity. International Journal of Science and Technology, 4(7), 312-327.
 
Maslov, A. V., Krupenin, M. T., & Gareev, E. Z. (2003). Lithological, lithochemical and geochemical indicators of paleoclimate: Evidence from Riphean of the Southern Urals. Lithology and Mineral Resources, 38 (5), 427-446,
https://doi.org/10.1023/A:1025575120343
 
Mazzullo, S. J., Boardman, D. R., Wilhite, B. W., Godwin, C., & Morris, B. T. (2013). Revisions of outcrop lithostratigraphic nomenclature in the Lower to Middle Mississippian Subsystem (Kinderhookian to Basal Meramecian series) along the shelf-edge in southwest Missouri, northwest Arkansas, and northeast Oklahoma. The Shale Shaker, 63(6), 414-454.
 
McLennan, S. M. (2001). Relationships between the trace element composition of sedimentary rocks and upper continental crust. Geochemistry, Geophysics, Geosystems, 2(4), 24.
https://doi.org/10.1029/2000GC000109
 
Meng, Q., Liu, Z., Bruch, A. A., Liu, R., & Hu, F. (2012). Palaeoclimatic evolution during Eocene and its influence on oil shale mineralisation, Fushun basin, China. Journal of Asian Earth Sciences, 45, 95-105.
https://doi.org/10.1016/j.jseaes.2011.09.021
 
Mohriak, W., & Talwani, M. (Eds.) (2000). Atlantic rifts and continental margins. American Geophysical Union, Washington, DC. 353p.
https://doi.org/10.1029/GM115
 
Munnecke, A., Calner, M., Harper, D. A., & Servais, T. (2010). Ordovician and Silurian sea-water chemistry, sea level, and climate: a synopsis. Palaeogeography, Palaeoclimatology, Palaeoecology, 296(3-4), 389-413.
https://doi.org/10.1016/j.palaeo.2010.08.001
 
Murphy, M. A., & Salvador, A. (1999). International stratigraphic guide-an abridged version. Episodes Journal of International Geoscience, 22(4), 255-271.
https://doi.org/10.18814/epiiugs/1999/v22i4/002
 
Nairn A. E. M., & Stahli, F. G. (1974). The occean basin and margins. The North Atlantic. Plenum Press, New York. Volume 2, 613p.
 
Nemcok, M. (2016). Rifts and passive margins. Structural Architecture, thermal Regimes and petroleum systems. Cambridge University Press. 620p.
https://doi.org/10.1017/CBO9781139198844
 
Odoma, A. N., Obaje, N. G., Omada, J. I., Idakwo, S. O., & Erbacher, J. (2013). Paleoclimate reconstruction during Mamu Formation (Cretaceous) based on clay mineral distributions. IOSR Journal of Applied Geology and Geophysics, 1(5), 40-46.
https://doi.org/10.9790/0990-0154046
 
Osokin, P. V. (1999). Central Asian phosphorite-bearing province (stratigraphy and phosphorite potential). Doctoral (Geology Mineral) Dissertation as a Scientific Report [in Russian]. GI SO RAN, Ulan-Ude.
 
Pettijohn, F. J., Potter, P. R. & Siever, R., (1987). Sand and sandstones. Springer, New York, 2nd Edition. 553p.
https://doi.org/10.1007/978-1-4612-1066-5
 
Ramkumar, M. U. (2015). Chemostratigraphy: Concepts, Techniques, Applications. Elsevier Radarweg, Amsterdam. 527p.
 
Ramkumar, M., Nagarajan, R., & Santosh, M. (2021). Advances in sediment geochemistry and chemostratigraphy for reservoir characterization. Energy Geoscience, 2(4), 308-326.
https://doi.org/10.1016/j.engeos.2021.02.001
 
Rangel, A., Parra, P., & Niño, C. (2000). The La Luna formation: chemostratigraphy and organic facies in the Middle Magdalena Basin. Organic Geochemistry, 31(12), 1267-1284.
https://doi.org/10.1016/S0146-6380(00)00127-3
 
Ratcliffe, K. T., Morton, A. C., Ritcey, D. H., & Evenchick, C. A. (2007). Whole-rock geochemistry and heavy mineral analysis as petroleum exploration tools in the Bowser and Sustut basins, British Columbia, Canada. Bulletin of Canadian Petroleum Geology, 55(4), 320-336.
https://doi.org/10.2113/gscpgbull.55.4.320
 
Reijers, T. J. A. (2011). Stratigraphy and sedimentology of the Niger Delta. Geologos, 2011, 17 (3): 133-162.
https://doi.org/10.2478/v10118-011-0008-3
 
Rimmer, S. M. (2004). Geochemical paleoredox indicators in Devonian-Mississippian black shales, central Appalachian Basin (USA). Chemical Geology, 206(3-4), 373-391.
https://doi.org/10.1016/j.chemgeo.2003.12.029
 
Roser, B. P., & Korsch, R. J. (1986). Determination of tectonic setting of sandstone-mudstone suites using SiO2 content and K2O/Na2O ratio. The Journal of Geology, 94(5), 635-650.
https://doi.org/10.1086/629071
 
Ross, D. J., & Bustin, R. M. (2006). Sediment geochemistry of the lower Jurassic Gordondale member, northeastern British Columbia. Bulletin of Canadian Petroleum Geology, 54(4), 337-365.
https://doi.org/10.2113/gscpgbull.54.4.337
 
Sarı, A., & Koca, D. (2012). An approach to provenance, tectonic and redox conditions of Jurassic-Cretaceous Akkuyu Formation, Central Taurids, Turkey. Bulletin of the Mineral Research and Exploration, 144(144), 51-74.
 
Shen, Y., Qin, Y., Wang, G. G., Guo, Y., Shen, J., Gu, J., Xiao, Q., Zhang, T., Zhang, C., & Tong, G. (2017). Sedimentary control on the formation of a multi-superimposed gas system in the development of key layers in the sequence framework. Marine and Petroleum Geology, 88, 268-281.
https://doi.org/10.1016/j.marpetgeo.2017.08.024
 
Short, K. C., & Stäuble, A. J. (1967). Outline of geology of Niger Delta. American Association of Petroleum Geologists Bulletin, 51(5), 761-779.
https://doi.org/10.1306/5D25C0CF-16C1-11D7-8645000102C1865D
 
Song, Y., Cao, Q., Li, S., Hu, S., Zhu, K., Ye, X., & Wan, L. (2021). Salinized lacustrine organic-rich shale influenced by marine incursions: Algal-microbial community, paleoenvironment and shale oil potential in the Paleogene Biyang Depression, East China. Palaeogeography, Palaeoclimatology, Palaeoecology, 580, 110621.
https://doi.org/10.1016/j.palaeo.2021.110621
 
Song, Y., Liu, Z., Sun, P., Meng, Q., & Liu, R. (2017). A comparative geochemistry study of several oil shale-bearing intervals in the Paleogene Huadian Formation, Huadian Basin, Northeast China. Journal of Earth Science, 28(4), 645-655.
https://doi.org/10.1007/s12583-016-0638-z
 
Sun, P., Sachsenhofer, R. F., Liu, Z., Strobl, S. A., Meng, Q., Liu, R., & Zhen, Z. (2013). Organic matter accumulation in the oil shale-and coal-bearing Huadian Basin (Eocene; NE China). International Journal of Coal Geology, 105, 1-15.
https://doi.org/10.1016/j.coal.2012.11.009
 
Sweere, T., van den Boorn, S., Dickson, A. J., & Reichart, G. J. (2016). Definition of new trace-metal proxies for the controls on organic matter enrichment in marine sediments based on Mn, Co, Mo and Cd concentrations. Chemical Geology, 441, 235-245.
https://doi.org/10.1016/j.chemgeo.2016.08.028
 
Tappan, H. (1968). Primary production, isotopes, extinctions and the atmosphere. Palaeogeography, Palaeoclimatology, Palaeoecology, 4(3), 187-210.
https://doi.org/10.1016/0031-0182(68)90047-3
 
Taylor, S. R., & McLennan, S. M. (1985). The continental crust, its composition and evaluation. Oxford: Blackwell.
 
Tribovillard, N., Algeo, T. J., Lyons, T., & Riboulleau, A. (2006). Trace metals as paleoredox and paleoproductivity proxies: An update. Chemical geology, 232(1-2), 12-32.
https://doi.org/10.1016/j.chemgeo.2006.02.012
 
Turner, B. W., Tréanton, J. A., & Slatt, R. M. (2016). The use of chemostratigraphy to refine ambiguous sequence stratigraphic correlations in marine mudrocks. An example from the Woodford Shale, Oklahoma, USA. Journal of the Geological Society, 173(5), 854-868.
https://doi.org/10.1144/jgs2015-125
 
Vishnevskaya, I. A., & Letnikova, E. F. (2013). Chemostratigraphy of the Vendian-Cambrian carbonate sedimentary cover of the Tuva-Mongolian microcontinent. Russian Geology and Geophysics, 54(6), 567-586.
https://doi.org/10.1016/j.rgg.2013.04.008
 
Von Eynatten, H., & Gaupp, R. (1999). Provenance of Cretaceous synorogenic sandstones in the Eastern Alps: constraints from framework petrography, heavy mineral analysis and mineral chemistry. Sedimentary Geology, 124(1-4), 81-111.
https://doi.org/10.1016/S0037-0738(98)00122-5
 
Von Rad, U., Hinz, K., Sarnthein M., & Seibold, E. (1982). Geology of the Northwest African Continental Margin. Springer, Berlin, 709p
https://doi.org/10.1007/978-3-642-68409-8
 
Wang, Z., Wang, J., Fu, X., Zhan, W., Armstrong-Altrin, J. S., Yu, F., Feng, X., Song, C., & Zeng, S. (2018). Geochemistry of the Upper Triassic black mudstones in the Qiangtang Basin, Tibet: Implications for paleoenvironment, provenance, and tectonic setting. Journal of Asian Earth Sciences, 160, 118-135.
https://doi.org/10.1016/j.jseaes.2018.04.022
 
Weber, K. J., & E.M. Daukoru, 1975. Petroleum geological aspects of the Niger Delta. Nigeria Journal of Mining and Geology, 12(1/2), 9-22.
 
Wei, W., & Algeo, T. J. (2020). Secular variation in the elemental composition of marine shales since 840 Ma: Tectonic and seawater influences. Geochimica et Cosmochimica Acta, 287, 367-390.
https://doi.org/10.1016/j.gca.2020.01.033
 
Wu, Y., Liu, C., Liu, Y., Gong, H., Awan, R. S., Li, G., & Zang, Q. (2022). Geochemical characteristics and the organic matter enrichment of the Upper Ordovician Tanjianshan Group, Qaidam Basin, China. Journal of Petroleum Science and Engineering, 208, 109383.
https://doi.org/10.1016/j.petrol.2021.109383
 
Xi, D., Wan, X., Jansa, L., & Zhang, Y. (2011). Late Cretaceous paleoenvironment and lake level fluctuation in the Songliao Basin, northeastern China. Island Arc, 20(1), 6-22.
https://doi.org/10.1111/j.1440-1738.2010.00753.x
 
Xin, B., Hao, F., Han, W., Xu, Q., Zhang, B., & Tian, J. (2021). Paleoenvironment evolution of the lacustrine organic-rich shales in the second member of Kongdian Formation of Cangdong Sag, Bohai Bay Basin, China: Implications for organic matter accumulation. Marine and Petroleum Geology, 133, 105244.
https://doi.org/10.1016/j.marpetgeo.2021.105244
 
Zeng, S., Wang, J., Fu, X., Chen, W., Feng, X., Wang, D., Song, C., & Wang, Z. (2015). Geochemical characteristics, redox conditions, and organic matter accumulation of marine oil shale from the Changliang Mountain area, northern Tibet, China. Marine and Petroleum Geology, 64, 203-221.
https://doi.org/10.1016/j.marpetgeo.2015.02.031
 
Zhang, L., Dong, D., Qiu, Z., Wu, C., Zhang, Q., Wang, Y., Liu, D., Deng, Z., Zhou, S., & Pan, S. (2021). Sedimentology and geochemistry of Carboniferous-Permian marine-continental transitional shales in the eastern Ordos Basin, North China. Palaeogeography, Palaeoclimatology, Palaeoecology, 571, 110389.
https://doi.org/10.1016/j.palaeo.2021.110389
 
Zhang, X., Gao, Z., Fan, T., Xue, J., Li, W., Zhang, H., & Cao, F. (2020). Element geochemical characteristics, provenance attributes, and paleosedimentary environment of the Paleogene strata in the Lenghu area, northwestern Qaidam Basin. Journal of Petroleum Science and Engineering, 195, 107750.
https://doi.org/10.1016/j.petrol.2020.107750
 
Zhu, B., Yang, T., Wang, J., Chen, X., Pan, W., & Chen, Y. (2022). Multiple controls on the paleoenvironment of the early Cambrian black shale-chert in the northwest Tarim Basin, NW China: Trace element, iron speciation and Mo isotopic evidence. Marine and Petroleum Geology, 136, 105434.
https://doi.org/10.1016/j.marpetgeo.2021.105434